This invention generally relates to monitoring the flow of parenteral fluid through a fluid delivery system to a patient and particularly to a method and system for detecting infiltrations or other fluid flow faults in a fluid delivery system.
Fluid delivery systems for infusing parenteral fluid to a patient having positive pressure pumps have become fairly common. Typically, the infusion pump is a peristaltic type pump wherein a plurality of rollers, cams, or cam-actuated fingers sequentially constrict a flexible tube filled with parenteral fluid. Such fluid delivery systems also include, in addition to the pump, an inverted bottle of parenteral fluid, an intravenous (IV) set comprising a drip chamber, which is secured to the bottle of fluid, clear plastic tubing attached to the discharge end of the drip chamber, and a cannula which is mounted on the distal end of the tubing and which is adapted to be inserted into the patient's blood vessel to thereby deliver parenteral fluid. Roller clamps to manually control fluid flow rates, injection sites and pressure diaphragms and the like may also be provided with the IV set.
One common problem with many of the commercially available systems is the difficulty in evaluating the fluid flow within the delivery system in order to detect proper fluid communication between the fluid delivery system and the patient's blood vessels. Generally, if a fluid flow fault develops, the infusion pump will continue to deliver parenteral fluid notwithstanding such fluid flow fault. Thus, for example, if a needle delivering the fluid to the patient becomes dislodged from the vein so that the discharge tip of the needle lies in adjacent interstitial tissue, the fluid, which continues to be pumped, infiltrates the interstitial tissue and may cause serious injury. If the needle becomes dislodged from the patient, i.e., an open line, there may be no immediate injury, but the patient does not receive the fluid or drugs needed for treatment. Infiltrations and occlusions generally are characterized by an increase in fluid pressure within the fluid delivery system. Unfortunately, there are many other events which can also produce pressure increases within the fluid delivery system. As a result, many of the prior monitoring systems, which were based on the fluid pressure exceeding a predetermined amount, could not discriminate between infiltration or occlusions and these other pressure increasing events.
Methods and systems described in U.S. Pat. No. 4,534,756 (Nelson) and U.S. applications Ser. No. 872,086, filed on June 6, 1986, and Ser. No. 872,199, filed on June 6, 1986, assigned to the present assignee were substantial advances in the art of monitoring the administration of parenteral fluids to a patient and particularly for detecting fluid flow faults in such systems. However, in many instances, such as with sedentary patients, the sophisticated level of fluid flow monitoring described and claimed in the above patent and patent applications is not needed.
What has been needed and heretofore unavailable is a rudimentary control system for monitoring the fluid flow in a fluid delivery system which can readily discriminate fluid flow faults, such as infiltrations and the like, from normal fluid flow variations during periods when significant pressure variations are not expected. The present invention satisfies that need.